The present invention relates to a multi-strike ink ribbon comprising a film substrate and an ink layer formed thereon, when necessary, with an adhesive layer interposed therebetween, which ink layer comprises as the main components (i) a resinous material and (ii) an ink component comprising an oil component which is not soluble in the resinous material and a coloring agent. More particularly, the present invention relates to a multi-strike ink ribbon having the above-mentioned structure, in which as an oil component a branched saturated primary alcohol, a fatty acid ester thereof or a hydroxy-fatty acid ester thereof is employed.
Recently a film-based multi-strike ink ribbon is replacing the conventional fabric ink ribbons in accordance with the recent wide-spread use of high speed typewriters and word processors, since the multi-strike ink ribbon is capable of yielding clearer, higher quality printed images free from background smearing as compared with the conventional ink ribbons.
Further, in accordance with the recent popularity of graphic pattern printing, there is a great demand for an ink suitable for forming solid black images, line images and thick line images with high image density, free from ink deposition on the background.
This demand stems from the shortcoming of a conventional ink that the background deposition of the ink is apt to occur when the image density is increased, because of the poor permeation into the printing paper and the poor fixing to the paper, so that the printing paper is smeared with the ink by a printing roller in the course of printing. This problem becomes more conspicuous when such a conventional ink is employed in a multi-strike ink ribbon, because in a multi-strike ink ribbon, the ink comprises an oil component and a coloring agent and the image fixing is carried out by the absorption of the ink by the printing paper. It is considered that an oil having a low viscosity will be effective for improving the permeation of the ink into the printing paper. However, when the resinous material employed in the ink layer is soluble in such an oil component, there is the problem that a sponge-like frame cannot be formed by the resinous material, so that a multi-strikable ink ribbon cannot be made.
Furthermore, a volatile oil which evaporates at room temperature and an oil which evaporates at high temperatures are not suitable for a multi-strike ink ribbon even if the evaporation is slight, since by such evaporation the density of the printed images is markedly decreased.
Under such circumstance, a multi-strike ink ribbon which meets the above recent demand has not been available yet.